In the recent topic, " [httpd] 'fastcgi param'..." , when I was trying to find examples for the OP, I had started reading this:
https://man.openbsd.org/bgplg.8 and so I wanted to try it,
well I also was using a old VM (qemu) but with OpenBsd63 on it, and had no success.
Then yesterday, I installed the current OpenBsd6.5 to the VM, and it just worked, using the examples in the above link.
The host system is also OpenBsd 6.5, but I depend on that, and do not like to experiment on it, so I use the VM for my experiments. So any way, just wanted to share, no real question or anything, but any one with comments, maybe additional tips, etc . would probably make this post / new topic more interesting. Now I have some chores to do.